1. Field of the Invention
The present disclosure relates to electrical machines, and more particularly to rotor hubs such as used in electrical generators, motors, and the like.
2. Description of Related Art
Rotors for permanent magnet (PM) machines generally come in two types, namely surface mount permanent magnet rotors and interior permanent magnet motors. For surface mount rotors, the magnets are installed on the surface of a magnetic steel rotor hub and a band is installed around the assembly to keep the magnets in position. For interior permanent magnet rotors, permanent magnets are embedded within the rotor of the machine which eliminates the necessity of the band and can have numerous advantages over surface mount PM machines.
There are many configurations for interior PM rotors, with different advantages and disadvantages for each. All configurations have a bridge section between each magnet that exists to mechanically hold the rotor together. The bridge sections, while structurally necessary, are pathways for magnetic flux leakage, where the magnetic flux between magnets effectively short circuits from magnet to magnet rather than crossing the air gap to the stator. This leakage flux represents a portion of the magnetic flux that does not perform useful work for the machine. The sizing of rotor bridges is therefore a critical design task—it must be small enough to minimize flux leakage, yet large enough to provide the structural strength necessary to hold the rotor together. Traditional PM rotors therefore must accommodate the leakage flux.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved PM machine rotors. The present disclosure provides a solution for this need.